A. Field of the Invention
The present invention relates to catalyzed hydrazine compound corrosion inhibiting compositions and their use in corrosive environments. More particularly, the present invention relates to compositions comprising a hydrazine compound, a catalytic organometallic complex which enhances oxygen scavenging, and preferably, a quinone compound which renders the composition compatible with chelating phosphonate scale control agents. The present invention further relates to the uses of these compositions either to inhibit or reduce corrosion or to remove oxygen.
B. Description of the Prior Art
It is well known to use hydrazine compounds for the removal of oxygen from gases and liquids to retard the corrosion of metal surfaces. Among the more important commercial uses of hydrazine compounds for this purpose are in water and steam apparatus such as boilers, hot water heating systems and water cooling systems. These hydrazine compounds are also used in inorganic and organic fluid heat exchange systems, e.g., alkylene glycol coolant systems. It is believed that the hydrazine compound reacts in the systems whereby the hydrogen from the hydrazine compound combines with the oxygen to form water or other compounds so as to bind up the oxygen and thereby inhibit corrosion.
The rate of reaction of a hydrazine compound, e.g., hydrazine, monomethyl hydrazine or the like, with oxygen at ambient temperatures or lower, is relatively slow. As a result, numerous suggestions have been made in the art to add catalytic or accelerating agents to the hydrazine compound or to modify hydrazine-containing systems to facilitate oxygen removal or scavenging in fluidic corrosive environments or to otherwise treat water systems. Thus various hydrazine compound systems have been suggested. Examples are described in U.S. Pat. Nos. 3,551,349 to Kallfass, 3,639,263 to Troscinski et al, 3,645,896 to Larsen, 3,687,610 to Gilson et al, 3,728,281 to Marks et al, 3,808,138 to Yamaguchi et al, 3,843,547 to Kaufman et al, and 3,983,048 to Schiessl et al, and in Japanese Kokai No. 155,048/75 assigned to Kurita.
In the two related patent applications mentioned above having the same inventor as herein, it was described that certain organometallic complexes, when used in combination with a hydrazine compound in corrosive environments, significantly increase the rate of reaction of the hydrazine compound in removing oxygen, even to a surprisingly significant degree at ambient or lower temperatures. In particular, the organometallic complexes described therein had not heretofore been taught or suggested in the prior art literature and are high performers as oxygen scavenging catalysts for hydrazine compounds. Further, the inclusion of the quinone compounds described in U.S. patent application Ser. No. 660,807 was discovered to additionally aid in the compatibility of these compositions with commercially used chelating phosphonate scale control agents in said corrosive environments.
Although the compositions described in these two patent applications are highly effective in removing dissolved oxygen from liquids and inhibiting corrosion of metals exposed to said liquids, certain impurities and inconveniences arise from their preparation. Specifically, in the making of the organometallic complexes, it was taught to react an inorganic salt of cobalt, manganese or copper (e.g., containing anions such as chloride, nitrate, bromide, iodide or sulfate) with certain organic ligands to obtain the catalytic complex. When these complexes are combined with the hydrazine compound (and preferably, in some instances, also with a quinone compound) to obtain the described corrosion inhibiting compositions, the anions in the inorganic salt were left as impurities in the final product.
In processes such as deoxygenation of feed water for low and medium pressure stream generators, the presence of these anions is judged to be harmless. However, in certain applications (e.g., in the feed water for high-pressure boilers having a pressure of about 1500 psig or more) the presence of these anions is undesirable because the tolerance to impurities in such systems is very low. Moreover, the employment of certain anions (e.g., nitrates) may cause a fire hazard to arise from mixing the inorganic salt with the hydrazine compound. For example, if cobalt nitrate hexahydrate is mixed in a certain ratio with hydrazine hydrate, the resulting solution may self-ignite upon heating at approximately 80.degree. C. Therefore, when a catalyzed hydrazine solution is to be prepared with the use of the above cobalt nitrate, it is a normal practice to first combine the hydrazine compound with the organic ligand and then add to them a dilute solution, preferably aqueous, of the above cobalt nitrate. However, this multi-step addition procedure and the prior dilution of the cobalt inorganic salt is not desirable on a large commercial production scale for cost and processing reasons. Instead, it would be more advantageous to employ a simplified method of addition of these three components with no prior dilution of any of them.